Thanks. New concerns about the ebola virus. No cure for it, and two Americans trying to help people in west Africa have contracted it. And bazzy Ka thatny has the latest. Reporter: Good morning. The Americans who have come down with ebola are cautious professionals who knew the risk but felt called to help as a truly terrifying disease spreads. Pick up one foot. Reporter: This is the kind of rigorous decontamination process in Africa's ebola hot zone, hazmat suits, disinfecting. Despite the precautions, two American health care workers fighting for their lives. Dr. Kent Brantley, who's Christian faith brought him here, head to toe protective suit still contracting the deadly disease. He's a servant and a doctor. And when you put that together, he's a man who cares about people. Reporter: And Nancy rightbull, a volunteer from Charlotte, North Carolina, who works at the isolation ward at the same hospital, the second American affected. They are isolated and receiving treatment. This ebola outbreak is deadly, killing 60% of those infected. It's spread to three countries in west Africa, making it the largest ebola outbreak ever recorded. If this is not confronted and contained in west Africa, it will be somewhere else. Reporter: And now a scramble to halt the disease in Lagos, Nigeria, the largest city in the country. A sick patient arrived on a plane and did not survive. That same passenger was weeks away from visiting the U.S. To visit family in Minnesota. This morning relief organizations are calling for international help and more prayer. Two other volunteers may have been exposed to the virus and are being closely monitored. Get more from Dr. Richard Besser. And, rich, we saw all the precautions they take, but that's no guarantee. It is no guarantee. Usually you'll get this in health care workers early on in the outbreak before all the infection control and the equipment. But this has been going on for five months. And I've worn this gear. And after 15 minutes, getting overheated and dehydrated. One of the riskiest times isn't with the patient, but come out and decontaminate you. Why is that? They have to spray down every layer of clothing with bleach. When you reach for another glove, you can get contaminated. One came to the United States before showing symptoms, they show no symptoms. What's the risk it's here? There is a risk. We have talked about malaria, many diseases that are imported. The way it could get here if someone traveled during the three week period before showing symptoms. The good news with this family, they left the country before he was showing signs of disease. S the chances of getting it is about zero. What's the most important thing to be done to contain this? They have to limit it. If it spreads into Nigeria, that's what we're hearing about, who knows how far this is going to go. This is the hardest outbreak of ebola ever for them to control.

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